Plating thickness regulator



Oct. 27, 1953 G. H. RENDEL PLATING THICKNESS REGULATOR Filed July 10, 1950 2 Sheets-Sheet l s Q' o s 4 l2 IIOttO.

INVENTOR GEORGE H.

RENDEL,

L74 JWXQXM ATTORNEY Oct. 27, 1953 G RENpEL 2,657,177

PLATING THICKNESS REGULATOR Filed July 10, 1950 2 Sheets-Sheet 2 INV ENT OR GEORGE H. RENDEL,

72 ATTORNEY Patented Oct. 27, 1953 PLATING THICKNESS REGULATOR George-H. Rendel, Mount Lebanon, Pa assign'cr to United States Steel Corporation, a corporation of New Jersey Application "July 10, 1950, Serial No. 172,855

3 Claims. 1

This invention relates to =Ja plating thickness regulator and :is a continuation-m-part of my copending application. Serial No. 31,772, filed June 8, 1948, now Patent No.- 2,603,595. The regulator is particularly designed to maintain specified electrolytically deposited tin coating on a moving strip by regulating the plating current applied to the strip. While such regulators are in commonuse, they are not particularly designed tooperate in conjunction with a plating thickness meter. Thus it is necessary to provide additional equipment if it is desired tocontinuously indicate the thickness of the tin.

vIt is therefore an object-of my invention to provide a plating thickness regulator which may be used in conjunction with the plating thickness meter.

This and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a schematic wiring diagram showing one specific embodiment of my invention; and

Figure 2 is a schematic wiringdiagram showing a second embodiment of my invention.

Referring more particularly to the drawings the reference numeral 2 indicates a plating tank containing an electrolyte. The strip S to be coated passes over a conductor roll 4 into the tank 2 and is directed by means of deflector rolls 6 between anodes 8 and Ill. The strip passes'out of the tank between rolls l2. Plating current is provided to the anode 8 bymeans 01 agenerator l4 and to anode 10 by means of an identical generator IG. The negative terminals-ofgenerators l4 and [6 are connected to the conductor roll 4 through their common lead l8 so that the strip S is maintained at cathode potential. The positive terminal of generator I4 is connected to the anode 8 through a lead and the positive terminal of generator l6is connected to the anode l0 through a lead 22. A shunt 24 in the line '20 and a shunt 26 in thelline 22 measure the plating current for anodes 8 and 10, respectively; The voltage drop across shunt 24 is proportional in amplitude to the current passing through line 20 and the voltage drop across shunt 26 isproportional in amplitude to the current passing through line 22. I

In my above identified copending application I use a totalizing shunt tomeasure thetotal plating current from generators l4 and 16. While this same arrangement might be used in the present application, I prefer to use the arrange ment shown in Figure 1. 'In this arrangement resistances 21 and 28 are connected to the terminals of shunt 24 by means of lead wires '29 and 30 and resistances 3| and 32 are connected to the terminals of shunt 26 by means of lead wires 33 and 34. The resistances 21 and II are connected to a lead wire and resistances 28 and 32 are connected to a lead wire 42. The resistances 21, 28, SI and '32 are preferably ot "the same ohmic value. The potential drop across lead wires 40 and 42 is used as the plating current reference in the same manner as the totalizing shunt is used in my copending application. The resistor network operates as i'ollows:

Assuming a current flow from generator l6 that causes a potential drop of 0.050 volt across the terminals of shunt 26 and zero current from generator 14 that results in zero .potential drop across the terminals of shunt 24, the potential drop between wires 33 and 34 will be 0.050 volt and there will be zero voltage drop between wires "and 30. The 0.050 volt drop between wires 33 and 34 will flow through resistors 21, 28, 3| and 32 thus causing a potential drop of 0.0125 across each of the four resistorswith a resultant potential of 0.025 volt appearing across wires 40 and 42.

If the current flow on generator [4 is increased until a potential drop of 0.050 volt appears across the terminals of shunt 24 while the current load through generator I6 remains unchanged, the potential drop between wires 33 and 34 and also between wires 29 and 30 is 0.050 volt. As indicated in Figure 1, wires 29 and 33' are'of like polarity and wires 30 and are also of like polarity. Since the potential drops across shunts Hand 26 are equal in amplitude and their interconnecting wires are connected to like polarity, there will be zero current flow throughresistors 21, 28, II and 32. Therefore, there is zero voltage drop across each of the resistors and the potential at wires 40 and 42 is 0.050 volt. In a similar manner a resistor network may be employed in combination with any number of current shunts to provide an accurate measurement of the sum of the currents flowing through all of the shunts.

The leads 40 and 42 are connected to a contact making galvanometer 44 through resistances 46 and 48. Connected in shunt across the terminals of resistance 46 is an adjustable potentiometer 50 and resistance 52.

A tachometer generator 54 is mechanically connected to the roll -2. Since the tachometer generator is driven at strip speed, it provides-a source of potential having an amplitude directly proportional to the speed of the strip through the plating tank. Tachometer generator 54 is connected to a voltage dividing network comprised of resistor 56, variable potentiometer 58, variable potentiometer 60 and resistor 62. The resistor 56 and potentiometer 58 are connected across the terminals of potentiometer 50 and are used-as ashunting means to provide adjustment tocompensate for changes in strip width. The potential drop across potentiometer 60 is ime pressed on the galvanometer 44 through lines 84 and 66. The adjustable arm 68 01' potentiometer 60 is mechanically connected to a split field reversible motor which is provided with power through the lines I2 and I4. Line 12 is connected to the movable element I6 of the gal vanometer 44. Two stationary contacts I8 and 80 are provided in the galvanometer and a circuit is completed to one of the fields of motor I0 depending upon which of the stationary contacts is contacted by the element 16. The direction of rotation of the motor I0 depends upon which of its fields BI is energized. The motor I0 is also mechanically connected to the arm 82 of a dial 84 which is calibrated to read from 0 to 1.5 in pounds of tin per base box. The movement of the arm 82 corresponds to the movement of the arm 68. 7

When the tinning line is not operating, the voltage'output from tachometer generator 54 and across lines 40 and 42 are zero so that no energy is impressed on the winding of galvanometer 44. Therefore, the contacts of galvanometer 44 will remain open and the arms 68 and 82 will remain in their attained position instead of indicating zero. Thus, it cannot be determined by looking at the dial 84 that the line is not in operation. If a continuous record is being kept, it will indicate that the line is operating at all times. In order to remedy this I provide a rectifier 80 having its rectified output applied across the resistor at through the lines 83 and 90. Located in the line 90 is a relay 92 having normally closed contacts 94 and a coil 88 which is energized when the line is operating. Alternating current is applied to rectifier 86 from the secondary winding of a transformer 98. The primary winding of the transformer 93 is energized from alternating current supply lines I00.

When the line is operating the coil 93 is energized, thus opening the contacts 94 so that no current is supplied through the lines 88 and 90 to potentiometer 00. When the line is at rest. the coil 98 is deenergized closing contacts 84 so that a direct current potential is applied across the potentiometer 88. This voltage energizes the winding of galvanometer 44, thus moving its pointer '16 in a direction to complete the circuit to the reverse winding of motor 10, which in turn, moves the contact arms 68 and 82 to the zero position. These arms are maintained in this position until the tinning line is started, when the normally closed contacts 94 are opened and the meter is restored to normal operation.

The plating thickness regulator including potentiometers I04 and H2 and exciter I28 is actuated from the plating thickness meter by mechanically connecting the motor III to the contact arm I02 of a potentiometer I04. The potentiometer IE4 is connected by means of wires I06 and 528 to a rectifier H0 which provides a substantially constant D. C. potential on wires I85 and I03. A second potentiometer H2 is connected to the rectifier H0 in parallel with potentiometer I04. Potentiometer H2 is provided with an operating arm H4 and a scale IIB calibrated to show coating thickness. The rectifier I I0 is connected to an A. C. power source by means of wires H8 and I20. Also connected to the wires I18 and I20 is a relay coil I22 which is provided with normally open contacts I22C and I22C. Energization of coil I22 is controlled by means of a start-stop switch I24. The normally open contact I 226 is provided in the line I08 to control the flow of current to potentiometers I04 and II2. Also connected to wires IIB and I20 is the motor I25 of aregula-ting exciter I28. The regulating at its obtained value.

4 exciter I28 has a self-excited field winding I30 which may be adjusted by means of a variable resistor I32 to provide sufiicient magnetization to maintain the electrical output of exciter I28 The exciter I28 also has a control field winding I34 which is connected to the contact arms I02 and H4 by means of wires 36 and I38, respectively. The output of exciter I28 is connected to the fields ME and IBF of generators I4 and I 6 through wires I40 and I42. The normally open contacts i220 are located in the wire I40. To insure stability of the regulating system an anti-hunting transformer I44 is employed in the conventional manner. The primary winding I46 of the transformer is connected across the wires I40 and I42 and the secondary winding I48 is connected to stabilizing field I50 or" the exciter I28. Adjustable resistors MR and may be connected in series with the field windings HF and IGF, respectively, to provide individual adjustment of plating generators I4 and I8. The operation of the device is as follows:

Assuming that the rheostats 50 and 58 are adjusted for plating current efiiciency and strip width and assuming that it is desired to deposit 0.75 pound coating on the strip S, contact arm 5. is adjusted to the point where the calibrated dial H8 indicates 0.75 which would result for example in contact arm H4 being positioned exactly midway on potentiometer H2. The startstop switch I24 is then closed, thus energizing relay coil I22 to close contacts I22C and I220. This completes the circuit from the rectifier IIO to potentiometers I04 and H2. Assuming that rectifier I I0 impresses I00 volts on wires I06 and 558 the voltage drop across potentiometers I94 and i 52 would be volts when the tinning line is in operation. Therefore, the potential of contact arm II4 will be 50 volts positive when referred to wire I06. Assuming that the tinning line is in the process of being started from rest, the indicating pointer 82 on dial 84 will indicate zero and the contact arm I02 will be positioned at the extreme end nearest wire I08. Therefore, a potential difierence of 50 volts will exist between contact arms I02 and I I4 which will cause current to i'iow through field winding I34 in the direction indicated by the solid line arrow to increase the voltage output of regulating exciter I20. As the potential of exciter I28 is raised, the voltage of plating generators I4 and I6 increases, thus causing an increase in current flow through the electrolytic bath. This causes motor :0 to rotate in a direction to move contact arm I02 away from wire IQS. The current in field winding I34 will continue to flow in the same direction but at a diminishing rate as contact arm 502 approaches the midpoint of potentiometer I04. When contact arm I02 reaches the midpoint of potentiometer I34, which corresponds to 0.75 pound per base box coating thickness, there will be a zero potential difierence between contact arms I02 and H4. Therefore, the current will stop flowing through field winding I34 and the voltage output from regulating exciter I28 is maintained at its attained value by the magnetizing current supplied by its self-excited field winding I30. If motor 70 moves contact I82 past the midpoint on potentiometer I04, the potential from contact IE2 to wire I06 will be at a higher positive potential than the potential between contact arm I I4 and wire I05. Therefore, current will fiow throu h field winding I34 in the opposite direction as shown by the broken arrow. This reduces the magnetizing forces in exciter I28 and lowers its potential output, thus reducing the excitation on generator fields HF and IBF to lower the current passing through the electrolytic bath. This in turn causes motor to rotate in a direction to reduce the potential difference between contact arms I02 and H4.

Figure 2 shows a second embodiment of my invention in which an electronic voltage regulator I52 is employed to control the magnetizing current in field winding I30 of the exciter I28. The electrical output of the electronic regulator I52 is controlled by the difference in polarity of the potential between contact arms I02 and H4. For example, when contact arm H4 is positive when referred to contact arm I02 the electrical output from regulator I52 is at its maximum and when contact I I4 is negative when referred to contact arm I02 the electrical output from regulator I52 is at its minimum. Thus electronic regulator I52 recognizes polarity and voltage unbalance between wires I36 and I38 and responds to this voltage difierence to control the field winding I30 of exciter generator I28 to eifect the plating current which will reposition contact arm I02 on potentiometer I04 to retain a balance of potential between wires I36 and I38. Otherwise, the construction and operation of this embodiment is the same as that of Figure 1.

While two embodiments of my invention have been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. Apparatus for controlling the amount of metal electrolytically deposited on an elongated longitudinally moving object comprising a gen erator for supplying current to said object, a field winding for said generator, means for obtaining a potential proportional to the speed of the object, means for obtaining a potential proportional to the output of said generator, means for comparing the said potentials, an electrical connection between each of the first two means and the comparing means, a potentiometer in one of said electric connections, a first contact arm for said potentiometer, means operable by said comparing means for restoring balance between the said potentials, said last named means including a reversible motor, electric means connecting said motor to said comparing means for operation of said motor in opposite directions in accordance with the direction of unbalance of the said potentials, a second potentiometer, power leads for connecting said second potentiometer to a source of D. C. power, a third potentiometer connected in parallel with the second potentiometer, a contact arm for each of said second and third potentiometers, means for connecting said motor to one of said second and third contact arms to move the same proportional to movement of said motor, an exciter for said field winding, electrical means connecting said second and third contact arms to said exciter, and means connecting said motor to said first contact arm to move the same proportional to the movement of said motor.

2. Apparatus for controlling the amount of metal electrolytically deposited on an elongated longitudinally moving object comprising a generator for supplying current to said object, a field winding for said generator, means for obtaining a potential proportional to the speed of the object, means for obtaining a potential proportional to the output of said generator, means for comparing the said potentials, an electrical connection between each of the first two means and the comparing means, a potentiometer in one of the said electric connections, a first contact arm for said potentiometer, means operable by said comparing means for restoring balance between the said potentials, said last named means including a reversible motor, electric means connecting said motor to said comparing means for operation of said motor in opposite directions in accordance with the direction of unbalance of the said potentials, a second potentiometer, power leads for connecting said second potentiometer to a source of D. C. power, a third potentiometer connected in parallel with the second potentiometer, a contact arm for each of said second and third potentiometers, means for connecting said motor to one of said second and third contact arms to move the same proportional to movement of said motor, an exciter for said field Winding, electrical means connecting said second and third contact arms to said exciter, means connecting said motor to the first said contact arm to move the same proportional to the movement of said motor, a scale for indicating thickness of the coating on said object, an indicating arm coacting with said scale, and means for connecting said indicating arm to said motor.

3. Apparatus for controlling the amount of metal electrolytically deposited on an elongated longitudinally moving object comprising a generator for supplying current to said object, a field winding for said generator, means for obtaining a potential proportional to the speed of the object, means for obtaining a potential proportional to the output of said generator, means for comparing the said potentials, an electrical connection between each of the first two means and the comparing means, a potentiometer in one of the said electric connections, a first contact arm for said potentiometer, means operable by said comparing means for restoring balance between the said potentials, said last named means including a reversible motor, electric means connecting said motor to said comparing means for operation of said motor in opposite directions in accordance with the direction of unbalance of the said potentials, a rectifier, a second potentiometer electrically connected to said rectifier, a third potentiometer connected in parallel with the second potentiometer, means in the connection from said rectifier to said second and third potentiometers for interrupting the fiow of current to said potentiometers, a contact arm for each of said second and third potentiometers, means for connecting said motor to one of said second and third contact arms to move the same proportional to movement of said motor, an exciter for said field winding, electrical means connecting said second and third contact arms to said exciter, means connecting said motor to the first said contact arm to move the same proportional to the movement of said motor, a scale for indicating thickness of the coating on said object, an indicating arm coacting with said scale, and means for connecting said indicating arm to said motor.

GEORGE H. RENDEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,325,401 Hurlston July 27, 1943 2,427,661 Cook Sept. 23, 1947 

1. APPARATUS FOR CONTROLLING THE AMOUNT OF METAL ELECTROLYTICALLY DEPOSITED ON AN ELONGATED LONGITUDINALLY MOVING OBJECT COMPRISING A GENERATOR FOR SUPPLYING CURRENT TO SAID OBJECT, A FIELD WINDING FOR SAID GENERATOR, MEANS FOR OBTAINING A POTENTIAL PROPORTIONAL TO THE SPEED OF THE OBJECT, MEANS FOR OBTAINING A POTENTIAL PROPORTIONAL TO THE OUTPUT OF SAID GENERATOR, MEANS FOR COMPARING THE SAID POTENTIALS, AN ELECTRICAL CONNECTION BETWEEN EACH OF THE FIRST TWO MEANS AND THE COMPARING MEANS, A POTENTIOMETER IN ONE OF SAID ELECTRIC CONNECTIONS, A FIRST CONTACT ARM FOR SAID POTENTIOMETER, MEANS OPERABLE BY SAID COMPARING MEANS FOR RESTORING BALANCE BETWEEN THE SAID POTENTIALS, SAID LAST NAMED MEANS INCLUDING A REVERSIBLE MOTOR, ELECTRIC MEANS CONNECTING SAID MOTOR TO SAID COMPARING MEANS FOR OPERATION OF SAID MOTOR IN OPPOSITE DIRECTIONS IN ACCORDANCE WITH THE DIRECTION OF UNBALANCE OF THE SAID POTENTIALS, A SECOND POTENTIOMETER, POWER LEADS FOR CONNECTING SAID SECOND POTENTIOMETER TO A SOURCE OF D. C. POWER, A THIRD POTENTIOMETER CONNECTED IN PARALLEL WITH THE SECOND POTENTIOMETER, A CONTACT ARM FOR EACH OF SAID SECOND AND THIRD POTENTIOMETERS, MEANS FOR CONNECTING SAID MOTOR TO ONE OF SAID SECOND AND THIRD CONTACT ARMS TO MOVE THE SAME PROPORTIONAL TO MOVEMENT OF SAID MOTOR, AN EXCITER FOR SAID FIELD WINDING, ELECTRICAL MEANS CONNECTING SAID SECOND AND THIRD CONTACT ARMS TO SAID EXCITER, AND MEANS CONNECTING SAID MOTOR TO SIAD FIRST CONTACT ARM TO MOVE THE SAME PROPORTIONAL TO THE MOVEMENT OF SAID MOTOR. 